本文基于 spring cloud gateway 2.0.1

1、简介

直接 获取 路 由 的 方法 是 通过 RouteLocator 接口 获取。 同样， 该 顶 级 接口 有多 个 实现 类，

RouteLocator 路由定位器，顾名思义就是用来获取路由的方法。该路由定位器为顶级接口有多个实现类，如类图所示，本节会对其实现类一一进行介绍。

通过类图可知，路由定位器接口有三种实现方法：

• RouteDefinitionRouteLocator 基于路由定义的定位器
• CachingRouteLocator 基于缓存的路由定位器
• CompositeRouteLocator 基于组合方式的路由定位器

2、RouteLocator 路由定位器

与上节学习的路由定义定位器接口类似，RouteLocator 路由定位器只有一个 getRoutes 方法，用来获取路由信息。

public interface RouteLocator {//获取路由对象Flux<Route> getRoutes();
}

2.1、Route 路由对象

Route 路由定义了路由断言、过滤器、路由地址及路由优先级等信息。当请求到达时，在转发到代理服务之前，会依次经过路由断言匹配路由 和 网关过滤器处理。

public class Route implements Ordered {//路由 Id private final String id; //路由地址 private final URI uri; //路由的优先级 private final int order; //路由断言，判断请求路径是否匹配private final AsyncPredicate<ServerWebExchange> predicate;//网关过滤器private final List<GatewayFilter> gatewayFilters;-----------------------省略-------------------------
}

3、 RouteDefinitionRouteLocator 基于路由定义的定位器

3.1、初始化

RouteDefinitionRouteLocator 构造函数有多个参数：路由定义定位器、路由断言工厂、网关过滤器及网关配置对象。 根据传入的参数，设置 routeDefinitionLocator 和 网关配置，并初始化路由断言 和 网关过滤器。 RouteDefinitionRouteLocator 的实现方式是基于路由定义来获取路由，它实现了 RouteLocator 接口，用来获取路由信息。

public class RouteDefinitionRouteLocator implements RouteLocator, BeanFactoryAware, ApplicationEventPublisherAware {protected final Log logger = LogFactory.getLog(getClass());private final RouteDefinitionLocator routeDefinitionLocator;private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap<>();private final Map<String, GatewayFilterFactory> gatewayFilterFactories = new HashMap<>();private final GatewayProperties gatewayProperties;private final SpelExpressionParser parser = new SpelExpressionParser();private BeanFactory beanFactory;private ApplicationEventPublisher publisher;public RouteDefinitionRouteLocator(RouteDefinitionLocator routeDefinitionLocator,List<RoutePredicateFactory> predicates,List<GatewayFilterFactory> gatewayFilterFactories,GatewayProperties gatewayProperties) {//设置路由定义定位器this.routeDefinitionLocator = routeDefinitionLocator;//初始化路由断言工厂initFactories(predicates);//初始化网关过滤器gatewayFilterFactories.forEach(factory -> this.gatewayFilterFactories.put(factory.name(), factory));this.gatewayProperties = gatewayProperties;}@Autowiredprivate Validator validator;@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {this.beanFactory = beanFactory;}@Overridepublic void setApplicationEventPublisher(ApplicationEventPublisher publisher) {this.publisher = publisher;}private void initFactories(List<RoutePredicateFactory> predicates) {predicates.forEach(factory -> {String key = factory.name();if (this.predicates.containsKey(key)) {this.logger.warn("A RoutePredicateFactory named "+ key+ " already exists, class: " + this.predicates.get(key)+ ". It will be overwritten.");}this.predicates.put(key, factory);if (logger.isInfoEnabled()) {logger.info("Loaded RoutePredicateFactory [" + key + "]");}});}--------------------------------省略---------------------------------
}

• 此种方式的路由获取是通过 RouteDefinitionRouteLocator 获取 RouteDefinition 并将路由定义转换成路由对象
• 这里的routeDefinitionLocator是CompositeRouteDefinitionLocator，它组合了InMemoryRouteDefinitionRepository、PropertiesRouteDefinitionLocator、DiscoveryClientRouteDefinitionLocator三个RouteDefinitionLocator。
• PropertiesRouteDefinitionLocator是直接使用GatewayProperties的getRoutes()获取，其是通过spring.cloud.gateway.routes配置得来。

3.2、RouteDefinition 转换成 Route 的流程

![image](

// RouteDefinitionRouteLocator.java

@Overridepublic Flux<Route> getRoutes() {return this.routeDefinitionLocator.getRouteDefinitions().map(this::convertToRoute)//TODO: error handling.map(route -> {if (logger.isDebugEnabled()) {logger.debug("RouteDefinition matched: " + route.getId());}return route;});/* TODO: trace loggingif (logger.isTraceEnabled()) {logger.trace("RouteDefinition did not match: " + routeDefinition.getId());}*/}private Route convertToRoute(RouteDefinition routeDefinition) {AsyncPredicate<ServerWebExchange> predicate = combinePredicates(routeDefinition);List<GatewayFilter> gatewayFilters = getFilters(routeDefinition);return Route.async(routeDefinition).asyncPredicate(predicate).replaceFilters(gatewayFilters).build();}

• getRoutes() ：根据传入的 RouteDefinitionLocator 获取路由定义对象，使用map方法将每个 RouteDefinition 转换为 Route。

• RouteDefinitionLocator#convertToRoute ：是具体的转换方法，转换过程中涉及到路由断言 和 网关过滤器的处理，最后构建为Route 对象。

• 此处网关过滤器处理包括两种，一种是默认过滤器，作用于所有路由；一种是指定路由的自定义过滤器。首先获取默认过滤器，根据过滤器名称获取对应的过滤器，最终转换成有优先级的OrderedGatewayFilter。

3.2.1、convertToRoute##combinePredicates

combinePredicates主要是对找出来的predicate进行and操作

private AsyncPredicate<ServerWebExchange> combinePredicates(RouteDefinition routeDefinition) {List<PredicateDefinition> predicates = routeDefinition.getPredicates();AsyncPredicate<ServerWebExchange> predicate = lookup(routeDefinition, predicates.get(0));for (PredicateDefinition andPredicate : predicates.subList(1, predicates.size())) {AsyncPredicate<ServerWebExchange> found = lookup(routeDefinition, andPredicate);predicate = predicate.and(found);}return predicate;}@SuppressWarnings("unchecked")private AsyncPredicate<ServerWebExchange> lookup(RouteDefinition route, PredicateDefinition predicate) {RoutePredicateFactory<Object> factory = this.predicates.get(predicate.getName());if (factory == null) {throw new IllegalArgumentException("Unable to find RoutePredicateFactory with name " + predicate.getName());}Map<String, String> args = predicate.getArgs();if (logger.isDebugEnabled()) {logger.debug("RouteDefinition " + route.getId() + " applying "+ args + " to " + predicate.getName());}Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);Object config = factory.newConfig();ConfigurationUtils.bind(config, properties,factory.shortcutFieldPrefix(), predicate.getName(), validator);if (this.publisher != null) {this.publisher.publishEvent(new PredicateArgsEvent(this, route.getId(), properties));}return factory.applyAsync(config);}

3.2.2、convertToRoute##getFilters

getFilters 主要是利用loadGatewayFilters获取filter，使用AnnotationAwareOrderComparator进行排序
loadGatewayFilters利用工厂方法，使用GatewayFilterFactory根据config 获取具体的GatewayFilter实例

@SuppressWarnings("unchecked")private List<GatewayFilter> loadGatewayFilters(String id, List<FilterDefinition> filterDefinitions) {List<GatewayFilter> filters = filterDefinitions.stream().map(definition -> {GatewayFilterFactory factory = this.gatewayFilterFactories.get(definition.getName());if (factory == null) {throw new IllegalArgumentException("Unable to find GatewayFilterFactory with name " + definition.getName());}Map<String, String> args = definition.getArgs();if (logger.isDebugEnabled()) {logger.debug("RouteDefinition " + id + " applying filter " + args + " to " + definition.getName());}Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);Object configuration = factory.newConfig();ConfigurationUtils.bind(configuration, properties,factory.shortcutFieldPrefix(), definition.getName(), validator);GatewayFilter gatewayFilter = factory.apply(configuration);if (this.publisher != null) {this.publisher.publishEvent(new FilterArgsEvent(this, id, properties));}return gatewayFilter;}).collect(Collectors.toList());ArrayList<GatewayFilter> ordered = new ArrayList<>(filters.size());for (int i = 0; i < filters.size(); i++) {GatewayFilter gatewayFilter = filters.get(i);if (gatewayFilter instanceof Ordered) {ordered.add(gatewayFilter);}else {ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1));}}return ordered;}private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {List<GatewayFilter> filters = new ArrayList<>();//TODO: support option to apply defaults after route specific filters?if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {filters.addAll(loadGatewayFilters("defaultFilters",this.gatewayProperties.getDefaultFilters()));}if (!routeDefinition.getFilters().isEmpty()) {filters.addAll(loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));}AnnotationAwareOrderComparator.sort(filters);return filters;}

4、 CachingRouteLocator 基于缓存的路由定位器

public class CachingRouteLocator implements RouteLocator {private final RouteLocator delegate;private final Flux<Route> routes;private final Map<String, List> cache = new HashMap<>();public CachingRouteLocator(RouteLocator delegate) {this.delegate = delegate;routes = CacheFlux.lookup(cache, "routes", Route.class).onCacheMissResume(() -> this.delegate.getRoutes().sort(AnnotationAwareOrderComparator.INSTANCE));}@Overridepublic Flux<Route> getRoutes() {return this.routes;}/*** Clears the routes cache* @return routes flux*/public Flux<Route> refresh() {this.cache.clear();return this.routes;}@EventListener(RefreshRoutesEvent.class)/* for testing */ void handleRefresh() {refresh();}
}

基于缓存的路由定位器比较简单和缓存路由定义定位器比较类似，只需要调用 RouteLocator# getRoutes 即可获取路由。

根据传入的路由定位器获取路由信息并存储到缓存中。通过监听 RefreshRoutesEvent 事件刷新缓存的路由信息。

5、 CompositeRouteLocator 基于组合方式的路由定位器

public class CompositeRouteLocator implements RouteLocator {private final Flux<RouteLocator> delegates;public CompositeRouteLocator(Flux<RouteLocator> delegates) {this.delegates = delegates;}@Overridepublic Flux<Route> getRoutes() {return this.delegates.flatMap(RouteLocator::getRoutes);}
}

组合方式的路由定位器，将实现 RouteLocator 接口的路由定位器组合在一起，提供获取路由的统一入口。

6、小结

RouteLocator 接口用于获取路由信息，其有三个实现类

• RouteDefinitionRouteLocator
• CompositeRouteLocator
• CachingRouteLocator

最终使用的是CachingRouteLocator，它包装了CompositeRouteLocator，而CompositeRouteLocator则组合了RouteDefinitionRouteLocator。

RouteDefinitionRouteLocator 与 RouteDefinitionLocator比较容易混淆，前者是一个RouteLocator（路由定位器），后者是一个RouteDefinitionLocator（路由定义定位器），前者的 RouteDefinitionRouteLocator 主要从后者获取路由定义信息。